1. Field of the Invention
The present invention concerns wires with fillings in the form of passivated, reactive metals (hereinafter called "cored wires") and their use.
2. Background Art
Pyrophoric metals (such as magnesium, calcium, aluminium and alloys thereof) raise particular problems as to their treatment and use, especially when they are in powdered particulate form. These metals are used in finely divided particulate form for the treatment, for example, the deoxidation, of iron and steel melts, for desulphurization of pig iron melts, for the preparation of particular alloys, and so on.
It is known from U.S. Pat. No. 4,209,325 and/or from U.S. Pat. No. 3,998,625 that pyrophoric metals may be diluted by the addition of from 10 to 50% by weight of particulate lime, aluminium oxide or silicon dioxide to reduce their flammability.
When coating pyrophoric metals with fused salts, in which primarily alkali metal chlorides or alkaline earth metal chlorides are used (U.S. Pat. Nos. 3,881,993, 4,186,000 or 4,279,641), special measures for the protection of parts of the installation and the environment are dictated by the presence of these chlorine-containing salts.
In DE 39 08 815 Al, a process is described for the passivation of pyrophoric metals, especially magnesium, with from 0.5 to 5% by weight of a s-triazine and/or guanidine derivate as the passivating agent, based on the weight of the metal. Such passivated finely powdered metals are distinguished by their favourable behaviour against ignition and are therefore especially suitable as a treatment agent in the desulphurization of pig iron. The disclosure of DE 39 08 815 Al is hereby incorporated by reference into the present disclosure.
For the treatment of iron melts, for example in foundry operations, in recent years the treatment of the melts with cored wires having a filling of corresponding components has been introduced and has been widely used.
Patent DE 39 24 558 Cl describes an agent in the form of a cored wire and a process for its production, the use of which consists in the treatment of cast iron melts with a magnesium containing silicon alloy. The advantage of the cored wire described above lies in the shifting of the developed form of the carbon in the cast iron towards a spheroidal graphite form, achieved by alloying from 5 to 30% by weight of pure magnesium and 0.1 to 5% by weight of rare earth metals. A further benefit lies in the replacement of the subsequent process steps of desulphurization, magnesium treatment and inoculation of the cast iron melt by a single treatment measure to be carried out at a single time.